Near-field communications (“NFC”) is a short-range wireless technology that allows detection and communication between powered active “initiator” devices and non-powered passive “target” devices. A passive target device is typically a very small sticker with no connected power source. Passive target devices receive power from a radio frequency (“RF”) field from an initiator device. Upon receipt of an RF field, the passive target device establishes a transponder relationship with the initiator device, and the passive target device can transmit information to the initiator device.
Wireless voice and data services are expanding beyond the limits of available dedicated cellular spectrum. Clearing new dedicated spectrum for cellular use is complex and expensive, especially in cases where legacy, interference-sensitive devices and services already occupy the spectrum or are sensitive to transmissions from such spectrum. A particularly challenging interference sensitivity case occurs between mobile devices, such as cellular telephones, that operate in proximity to pacemakers and other medical devices, high definition televisions and other consumer electronics, and global positioning sensor (“GPS”) receivers. In this case, regulators should plan and fund the replacement of these legacy devices before selling spectrum or find spectrum buyers that are willing to wait years to put purchased spectrum to use. These cases limit regulator opportunity to sell spectrum (filling government coffers) and they limit cellular operator and device vendor access to much needed spectrum to meet subscriber demands. In order to support such dramatic growth, cellular operators, device vendors and regulators are now looking beyond traditional dedicated spectrum options. Shared spectrum use has some cost and resource efficiency advantages, especially in cases where demand is temporary and dynamic. Where demand is temporary, it is sometimes advantageous to use spectrum on a temporary basis rather than making a permanent investment in such spectrum. Unfortunately this shared spectrum option has similar technical challenges as dedicated spectrum clearing—that is, there is currently no practical and cost-effective means to identify and protect interference-sensitive devices from nearby cellular transmissions without replacement.